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Mesoscopic Diffusion of Poly(ethylene oxide) in Pure and Mixed Solvents
We present results from an experimental
dynamic light-scattering study of poly(ethylene oxide) (PEO) in both
a pure solvent (water) and a mixed solvent (tert-butanol + water). The concentration dependence
of the diffusive relaxation of the PEO molecules is found to be typical
of polymers in a good solvent. However, the mesoscopic diffusive behavior
of PEO in the mixed solvent is very different, indicating an initial
collapse and subsequent reswelling of PEO caused by co-nonsolvency.
Furthermore, in the solutions of PEO with very large molecular weights,
we found additional hydrodynamic modes indicating the presence of
PEO clusters and aggregates similar to those found by some other investigators